The present invention relates to a hydraulic press, and more particularly to a hydraulic press having adjustable supports for providing a platen surface thereof with a predetermined configuration during the pressing operation.
Known hydraulic presses may often be referred to as either of two basic types. In the one type they have a heavy frame, generally consisting of parallel frames made from steelplate with a fixed platen or table, and a movable platen or table actuated by force generating means. The other type includes two heavy plate or pressure beam structures, each of which can carry or form a platen or press table. The structures can be moved towards, or away from each other with the aid of force-generating means and yokes or C-shaped links. Although hereinafter briefly described, FIGS. 1a, 1b and FIG. 2 in the accompanying drawing are preliminarily referred to in this connection.
In FIG. 1 there are illustrated plate frames 1 with top portions 3 and bottom portions 5, while the numerals 7 and 9 respectively denote a fixed and movable platen, the latter being actuated by hydraulic cylinders 11. In FIG. 2 the numerals 21 and 23 respectively denote top and bottom pressure plate structures with respective top and bottom platens 25 and 27, while 29, 31 denote a yoke keeping the pressure plates 23 and 21 together. The plates 21 and 23 can be urged towards each other with the aid of the yoke and hydraulic cylinders 33.
When forces are applied with the aid of the corresponding hydraulic cylinders the FIG. 1a frames 1 and the FIG. 2 members 21, 23 deflect in a manner exaggeratedly illustrated in FIGS. 3 and 4, respectively. In many cases this results in considerable drawbacks, e.g. in pressing records which must have a very uniform thickness, moulding goods in moulds which must be kept parallel, deep-drawing sheet in presstools, shearing, edge folding of plates, tubes etc.
Different measures have been proposed for reducing the deflection exemplified in FIGS. 3 and 4. The frames, pressure beam structures etc. can be made very stiff by increasing their material content, but this is an expensive solution that also increases the weight of the press. The surfaces can also be given an initial curvature by uneven heating of the frames, such as to keep deflection within acceptable limits when the force is applied. This is however a solution that is relatively expensive, especially from an operational standpoint and is furthermore only usable in a restricted number of applications. It has also been suggested to float the platen on a hydrostatic bed, which likewise is an expensive solution in this case also requiring extra safety measures.